Deepwater wellheads of oil and gas wells are generally put in place by lowering a drill string having a bit at the bottom, boring hole in the ocean floor, and lowering a wellhead apparatus down the drill string. A large-diameter length of pipe is generally secured to the bottom of the wellhead, lowered into the drilled hole and centered therein.
Housing for wellhead equipment may consist of a subsea caisson having an open bottom that is lowered to the ocean floor and a pressure displacement dredging system to remove the soil inside the caisson. Such a device is set forth in U.S. Pat. No. 4,558,774 issued on Dec. 17, 1985. However, in this patent, apparatus in the caisson is used to remove the soil against its inner walls which eliminates soil friction inside the caisson which is positioned below the ocean floor.
It is also recognized that ship anchors have been positioned in the ocean floor by sucking them into the ocean floor in accordance with the method and apparatus disclosed in U.S. Pat. No. 4,432,671 issued on Feb. 21, 1984. However, the apparatus of this invention requires the use of a specially designed underwater motor-driven pump together with power-transmission cables which are removably connected to the anchor prior to installing the anchor in the ocean floor, and subsequently remotely disconnected from the anchor for removal to the ocean surface.
It is an object of the present invention to provide a well base structure that is highly stable, capable of taking high vertical and lateral loads, and can be controlled during installation to be either truly plumb or positioned at a predetermined angle relative to the vertical. Another object of the present invention is to provide an underwater wellhead apparatus that can be transported to the drilling location on a relatively small vessel and lowered to the ocean floor by means of a running pipe string. The apparatus, upon being positioned on the ocean floor, is subsequently sucked into the ocean floor by means of circulating fluid, such as water, down the running pipe string to actuate a suction device carried by the wellhead apparatus. The apparatus is anchored in the ocean floor by frictional resistance against both the internal and external walls of the apparatus. The apparatus is further provided with means whereby a well may be drilled through it into the ocean floor.